In endothelial cells (EC) NF-kB is the main transcription factor involved in the upregulation of the majority of pro-inflammatory genes expressed during EC activation, i.e., adhesion molecules, cytokines/chemokines and procoagulant factors. Expression of these genes plays a key role in the initiation of immune responses by targeting circulating leukocytes to sites of microbial invasion. Uncontrolled expression of pro-inflammatory genes can result in vascular thrombosis and tissue necrosis, such as what is observed during chronic inflammation, ischemia-reperfusion injury, septic shock and allograft or xenograft rejection. It is generally assumed that NF-kB transcriptional activity is regulated by controlling the translocation of NF-kB dimers from the cytoplasm to the nucleus. Once in the nucleus, it is believed that NF-kB dimers bind to specific DNA consensus sequences, where they act as transcriptional activators. The principal investigator presents evidence suggesting that nuclear translocation and DNA binding are essential, but not sufficient for, NF-kB transcriptional activity. In EC, the transcriptional activity of NF-kB is tightly regulated by an additional signaling pathway involving the activation of MAPK, activating NF-kB dimers directly or indirectly. Specifically, the investigators provide evidence that the transcriptional activity of RelA is dependent upon the activation of the atypical protein kinase Czeta. and p21ras. Furthermore, they present evidence suggesting that cAMP-dependent Protein Kinase (PKA) has a bimodal function in regulating NF-kB activity in EC. It is the aim of this proposal to study identified kinase modules, further identify the kinases involved in the phosphorylation and activation of NF-kB and to identify the exact level of the kinase cascade at which the interaction with RelA occurs. By addressing these specific aims, the principal investigator hopes to provide new insights concerning the regulation of the transcriptional activity of NF-kB in EC and its contribution to inflammation.